1. Field of the Invention
The present invention relates to a magnetic transfer method and apparatus for magnetically transferring data borne on a master medium to a slave medium.
2. Description of the Related Art
Generally speaking, with regard to magnetic storage mediums, there is a demand for increased storage capacity and low cost. Further desired are so-called high-speed access mediums, which are capable of advantageously reading out the data of a desired location in a short time. Examples of these mediums include hard disks and HD (high-density) flexible disks; so-called tracking servo technology, wherein the magnetic head accurately scans a narrow width track to achieve a high S/N ratio, plays a substantial role in attaining the high storage capacity thereof. A servo signal, address data signal, replay clock signal, etc., used for tracking within a certain interval occurring in one rotation of the disk are “preformatted”, that is, recorded on the disk in advance.
The magnetic head is set so as to be capable of reading out the preformatted signals and correcting its position thereby, whereby the magnetic head can accurately scan the track. According to the currently available preformatting technologies, one disk at a time, one track at a time is recorded by use of a specialized servo recording apparatus.
However, because the servo recording apparatuses are expensive and the preformatting operation consumes a considerable amount of time, this process accounts for a significant portion of the manufacturing costs incurred in producing preformatted disks; a reduction of said costs is desirable.
Meanwhile, methods of utilizing magnetic transfer to achieve this objective, not writing one preformatting track at a time, have been proposed.
According to magnetic transfer technologies, a master medium and a slave medium are brought into close contact, and while maintained in this state of close contact, a transfer magnetic field is applied thereto, whereby a magnetic pattern corresponding to the data (e.g., a servo signal) borne on the master medium is transferred to the slave medium. Magnetic transfer methods have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544, and 10(1998)-269566. According to the magnetic transfer occurring in these methods: a master medium having an uneven pattern corresponding to the data to be transferred to the slave medium, which is a magnetic transfer receiving medium such as a magnetic disk or the like, is prepared; this master medium is brought into a state of close contact with the slave medium; then, because by applying a transfer magnetic field, the magnetic pattern corresponding to the data carried by the uneven pattern (e.g., a servo signal) of the master medium is transferred to the slave medium, the preformatting can be performed without changing the relative positions of the master medium and the slave medium—that is, while the two media remain stationary; and not only is it possible to perform an accurate recording of the preformat data, it becomes possible to do so in an extremely short time.
Note that the transfer magnetic field is applied to a conjoined body formed of a slave medium and a master medium(s) brought into close contact with one surface or both surfaces of the slave medium, by use of a magnetic field generating means employing an electromagnetic or permanent magnet apparatus (es), which is disposed on one or both sides of the conjoined body. When the transfer magnetic field is applied, the conjoined body, formed of the master medium(s) and the slave medium that have been brought into and maintained in close contact, or the magnetic field is rotated relative to each other, whereby a magnetic pattern is transferred to the track on the circumference of the disk shaped slave medium(s).
However, according to the magnetic transfer method described above, in order to improve the degree of accuracy with which the magnetic pattern corresponding to the transfer data borne on the uneven pattern formed on the data bearing surface of the master medium is transferred and recorded onto the recording surface of the slave medium, it is necessary that the transfer magnetic field be applied be applied in the track direction while the data bearing face of the master medium and the slave surface of the slave medium are maintained in a close-contact state.
However, in actuality, it is difficult to generate the magnetic field to be applied by the magnetic field generating means so that it is parallel with the track direction over the entirety of the area encompassing the inner to the outer circumference of the slave surface of the slave medium; a portion of the magnetic field generated leaks into the surrounding vicinity. If the intensity of the portion of the transfer magnetic field that is leaked is high, the correct magnetic pattern to be transferred to and recorded on the slave medium becomes distorted, whereby an accurate transfer cannot be performed; for cases in which the transfer data is a servo signal, a problem arises in that an adequate tracking function cannot be obtained, and the reliability is thereby reduced.
In particular, for cases in which the magnetic pattern has been recorded on a single slave medium, unless a magnetic field of the intensity of the magnetic coercive force Hcs of the slave medium is used, the magnetic pattern will not become distorted; however, it has been clearly determined that when the slave surface of the slave medium is brought into contact with the data bearing surface of the master medium, which has the uneven pattern, the magnetic field is concentrated by the uneven pattern, so that a magnetic field having approximately ½ of the magnetic coercive force Hcs distorts the magnetic pattern.